? lost Aircraft (UK to U.S. with UK WW2 technology)

[FrankieS]

Hi all,

I'm possibly wrong, sorry in advance,

but I seem to remember (erroneously?)
that I read somewhere that before (or during/after?) the
true Tizard WW2 mission September 1940

(The team arrived in Halifax, Canada, on 6 September on board the CPR Liner Duchess of Richmond (later known as the RMS Empress of Canada), and went on to Washington, D.C., a few days later.)

there were different technological items supposed to be shipped
from UK to U.S. or Canada by an aircraft, which however crashed into the Atlantic ???

I thought this was mentioned

either in Kai Bird: American Prometheus
or in Richard Rhodes: Making of the Atomic Bomb

but didn't find it using search function on pdf's of the two books.

Does somebody know of such an incident or similar circumstances ?

thank You,
FrankieS